This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-173018, filed Jun. 18, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to the structure of a capacitor, and, more particularly, to suppression of the deterioration of a capacitor originated from the deterioration of a dielectric film which constitutes a capacitor film.
As the microfabrication of semiconductor devices such as DRAM and FRAM progresses, the cell area becomes smaller, making it difficult to secure the capacitance of capacitors that is demanded for storing data.
As one solution to this problem, in the case of DRAMs, for example, an attempt has been considered which gains a greater capacitance for the same capacitor area by using a high-dielectric substance such as BSTO having a higher dielectric constant than that of a silicon oxide film or silicon nitride film, which has conventionally been used as a capacitor film.
The fabrication of semiconductor devices requires that annealing in a hydrogen-containing atmosphere (hereinafter called xe2x80x9chydrogen annealingxe2x80x9d) after a multi-layer interconnection step in order to eliminate a plasma damage caused by the multi-layer interconnection step after forming a capacitor, thereby providing excellent transistor characteristics and leak characteristic. This hydrogen annealing is also called xe2x80x9csinteringxe2x80x9d.
It however became apparent that high-dielectric substances such as BSTO, or ferroelectric substances such as PZT have a low resistance to hydrogen annealing so that hydrogen annealing significantly deteriorates their film qualities. One possible cause for this deterioration is that hydrogen works as a reducing agent to reduce BSTO or PZT containing oxygen in hydrogen annealing.
This deterioration of a dielectric film which constitutes a capacitor film is likely to degrade the capacitor characteristics.
Accordingly, it is a primary object of the present invention to provide a capacitor whose structure is capable of restraining the deterioration of a dielectric film even when annealing is performed in a hydrogen-containing atmosphere, and a semiconductor device having this capacitor.
It is another object of the present invention to provide a semiconductor device having a circuit structure which can suppress the deterioration of a data retaining characteristic.
To achieve the first object, according to one aspect of this invention, there is provided a semiconductor device comprising:
one electrode formed above a semiconductor substrate or a plurality of dispersion electrodes formed in a dispersed manner above a semiconductor substrate; and
a plate electrode facing the one electrode of dispersion electrodes via a dielectric film and including a lower conductive layer formed on the dielectric film, a barrier layer formed on the lower conductive layer and an upper conductive layer formed on the barrier layer.
In this semiconductor device, the plate electrode includes the lower conductive layer, the barrier layer and the upper conductive layer. This plate electrode faces the one electrode or dispersion electrodes via the dielectric film and is one constituting element of a capacitor. Various materials can be selected for the barrier layer included in the plate electrode, regardless of the insulating property and the conductivity. For example, using a reducing material or a material which has a fine film quality for the barrier layer can reduce the amount of the reducing agent that reaches the dielectric film. Even if a material whose film quality is deteriorated by reduction is used for the dielectric film, therefore, the degradation of the dielectric film can be restrained. Even when annealing is performed in an atmosphere containing a reducing agent, therefore, it is possible to suppress the degradation of the dielectric film.
To achieve the second object, according to another aspect of this invention, there is provided a semiconductor device comprising:
memory cells each having a cell capacitor which includes a storage electrode and a plate electrode facing the storage electrode via a dielectric film;
a circuit for generating a potential to be applied to the plate electrode; and
a capacitor connected in series between an output terminal of the circuit and the plate electrode.
This semiconductor device has the capacitor connected in series between the output terminal of the circuit, which generates a potential to be applied to the plate electrode, and the plate electrode. This capacitor absorbs noise which is produced by memory cells at the time of data access. This makes it hard for that noise to go outside.
The capacitor also absorbs noise which is produced outside the memory cells. This makes it difficult for that noise to reach the plate electrode, thereby suppressing the deterioration of the data retaining characteristic that is originated from the noise applied to the plate electrode.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.